# Comparison of Optimal and Excess Fresh Gas Flow for Pre-intubation Oxygenation: A Randomized, Participant-Blind, Non-inferiority Study

## TL;DR

This study compares two methods of oxygen delivery before intubation and finds they are equally effective for reaching target oxygen levels.

## Contribution

The study demonstrates that optimal fresh gas flow is non-inferior to excess flow for pre-intubation oxygenation using machine-delivered ventilation.

## Key findings

- Both optimal and excess FGF groups achieved similar FeO2 levels at three and five minutes.
- The time to reach FeO2 of 85% was not significantly different between the two groups.
- Three minutes was insufficient to achieve FeO2 of 90% with the closed circuit system.

## Abstract

Background: The effect of different fresh gas flow (FGF) on achieving the target expired oxygenation (FeO2) has been evaluated mainly with manual bag-mask ventilation, which provides variable minute ventilation (MV). The effect of machine-delivered consistent MV has yet to be well established. The present study evaluated the efficacy of pre-intubation oxygenation using optimal and excess FGF.

Methods: One hundred adult patients aged 18-60 years and with American Society of Anesthesiologists' physical status I-III were randomized to receive optimal FGF (=MV+500 mL) or excess FGF (i.e., +50%) for pre-intubation oxygenation targeted to FeO2 of 85% and 90% or ventilated to maximum for five minutes. Concurrent fixed dial settings of volatile agents were used. Ventilation was done using an anesthesia machine in a pressure support (PS)-based technique. MV, fraction of inspired oxygen (FiO2), and FeO2 were collected and compared at different timepoints.

Results: Both optimal and excess FGF groups showed similar efficacy in achieving FeO2. The mean FeO2 in the optimal and excess group at three minutes was 84.52 ± 3.38% versus 84.94 ± 3.73%; p = 0.368, while the same at five minutes was 86.02 ± 3.12% versus 85.98 ± 3.57%; p = 0.615. The mean time required to achieve an FeO2 of 85% was 160.16 ± 67.15 seconds in the optimal FGF group and 147.81 ± 55.50 seconds in the excess FGF group (p = 0.335), with a mean difference of 12.35 seconds (8.36%).

Conclusion: Pre-intubation oxygenation using the optimal FGF is non-inferior to excess FGF, and is as adequate as using excess FGF to achieve FeO2 levels exceeding 85% during machine-delivered PS-based ventilation. However, it was noted that three minutes was insufficient to achieve the target FeO2 90% using a closed circuit system and concurrent volatile agents.